The development of the Breast Cancer Research Program (BCRP) of the Pittsburgh Cancer Institute (PCI) is an important extension of the rapid development and growth of the PCI, from its inception little more than eight years ago into one of the major NCI-designated comprehensive cancer centers. Several key features of the PCI and its environment at the University of Pittsburgh provide a strong foundation for development of the proposed BCRP: a) strong institutional commitment to development of an extensive translational research program for breast cancer as well as for other types of cancer, with recruitment over the past several years of a large number of relevant faculty members plus a commitment to recruit several more key personnel; b) an extensive clinical base for breast cancer research, including two University-affiliated hospitals and five surrounding satellite screening facilities, accounting for a total of 36,000 screening/diagnostic patient contacts per year and over 500 new cases of breast cancer annually; c) PCI's organizational structure and approaches that are highly oriented towards facilitation of high quality translational research, with direct leadership of PCI's director in the development of the program; and d) the Headquarters of the NSABP being located at the University of Pittsburgh, providing the direct potential for extension to group-wide investigation of promising new strategies that arise from the PCI BCRP. A major emphasis of the BCRP will be the study of the complex interactions of genetic, endocrine and environmental factors, which affect the differentiation and growth of breast tissues and the initiation and progression of breast cancer. The large number of PCI investigators with interests and research activities related to breast cancer have been organized into six research components: clinical and experimental therapeutics, cancer control and epidemiology, environmental, endocrine and pathology, immunology and molecular biology, and behavioral medicine and psychosocial. To facilitate the optimal development of the PCI BCRP, the major emphasis will be on fostering interactions and collaborations among a wide array of basic and clinical investigators, establishing a specialized tissue bank for optimal collection and processing of breast tissues for all of the required research needs and, most importantly, supporting the pilot phase of translational research projects that are considered most likely to provide new insights into the pathogenesis and progression of human breast cancer, that can be applied to the prevention diagnosis and/or treatment of women with breast cancer.